1. Field of the Invention
The present invention relates to an embedded memory device. In particular, this invention relates to an embedded memory device and a manufacturing method thereof that uses an integrated circuit manufacturing process to enhance stability of the voltage.
2. Description of the Related Art
For the industrial technology, an electronic system can be integrated into a single chip—named as system on chip (SOC). The SOC is manufactured by an integrated circuit manufacturing process, and the SOC is composed of a processor, an embedded memory, a variety of peripheral interfaces and external bus interfaces. During the evolution of technology, the development of SOC let the system designer can reduce the dimension occupied by the electronic system and the testing time. The reliability of the SOC is enhanced, and the developing time of the SOC is reduced.
The embedded memory is an important electronic element for the SOC. Reference is made to FIGS. 1A and 1B. FIG. 1A is a top view of the circuit layout of the embedded memory of the prior art. FIG. 1B is a cross-sectional view of the circuit layout of the embedded memory of the prior art. In FIG. 1A, the embedded memory circuit includes a core circuit 10, a grounding ring 12, and a power ring 14. From FIG. 1B, the core circuit 10 is composed of an ion distributing layer 100, a polysilicon layer 102, a first metal layer 104, a second metal layer 106, a third metal layer 108, and a fourth metal layer 110.
In SOC, because the change of operation status of the integrated circuit and the influence of the coupled capacitors between circuits, the power source oscillates varying. The unstable power source makes the voltage exceeded the range of the timing model and then the reliability of the circuit is reduced. As the circuit is developed to the deep sub-micron, the oscillation of the power source will probably make the transistor operates deviated from the normal saturation area, and the circuit function is failed. In the deep sub-micro of SOC, the dimension of the embedded memory occupies the chip area becoming higher. Therefore, the stable power source can increase the stability of the embedded memory, so that the yield rate of the SOC increases.